Field
The invention relates to a condenser, and more specifically, to a radiating module in a condenser which is in parallel connection with an air cooled island and is used for evaporative condensing the steam exhausted from the stream turbine.
Description of the Related Art
A direct air cooled unit employs air as the cooling medium to cool the exhausted stream from the turbine. Since air has a low density, a low specific heat capacity, and a low heat transfer coefficient, the provided temperature rise at the air side of the air cooled system is much higher than in the water cooled system, and the design back pressure at the air side of the air cooled system is also higher than in the water cooled system. This will greatly affect thermal efficiency of the unit. There are some problems, as follows, commonly existing in the actual operation of the air cooled unit. Firstly, the operational back pressure will rise when the air cooled system is contaminated, which adversely affects the economical efficiency. Secondly, the large variation range of the back pressure during the operation of the air cooled unit degrades the security and reliability of the unit operation. Thirdly, the operational back pressure of the unit depends highly on environmental factors, and therefore, the unit will experience a high load due to a high back pressure during high environmental temperature. To solve these problems, an auxiliary water cooled system is commonly used to improve the heat exchange capacity of the air cooled system so as to ensure the safety and economical efficiency of the unit, such as a mist cooled system, a parallel water-tower condenser water cooled system, a tandem evaporative condenser system. The evaporative condenser is a novel cooling device, which has been widely used in the field of refrigeration and chemical engineering industry, and has been used as a condenser for exhausted steam from the low pressure cylinder of the steam turbine in a small-scale unit, but is still under development for large-scale unit. The evaporative condenser as applied in the power station condensing system is quite different from that used in the refrigeration system in technical respect. The following aspects in the system and structural design should be taken into consideration. In the case that a peak-load evaporative condenser in parallel connection with a direct air cooled system is used to cool a portion of the exhausted steams, it is not applicable to employ tens of unitary evaporative condensers for a large-scale unit due to a large foot print resulting from the large scale of equipments, and due to high requirements on large cooling heat capacity and on ventilation height. The tube bundles for the refrigeration system are usually designed as coiled tubes, which is not applicable for cooling the exhausted stream from a turbine which has a large specific heat capacity due to its large frictional drag on the way. The frictional drag should be reduced in the case of application of an evaporative condenser in a power station condensing system, so as to reduce the operational back pressure of the unit and raise the operational efficiency. In the case of a peak-load evaporative condenser in parallel connection with a direct air cooled system, the vacuum system of the turbine will inevitably experience air leakage because of the negative pressure inside the tubes of the system.